NATURAL HAZARD IMPACT ANALYSIS AND PRIORITIZATION

The analysis of risk and prioritization of natural hazards requires:

  • Consideration of past experience with the hazard based on historical evidence and records (frequency).
  • Consideration of the physical attributes and size of the area impacted (Area)
  • Consideration of the scope or extend of the possible damage and loss (Magnitude).

The following process is one of many that can be used to estimate the impact each hazard on the county.

CRITERIA:

The analysis of the three criteria: frequency, area impacted, and magnitude

are based on a scale of from 1 (lowest) to 5 (highest)]

1.FREQUENCY

1Hazard Occurs less than once every 100 years.

2Likely to occur at least every 100 years.

3Likely to occur at least every 50 years.

4Likely to occur every 10 years

5Yearly

2.AREA IMPACTED

1Impacts one specific location (a city block, Coupeville or

Langley, Freeland)

25 – 10 square miles (all of Oak Harbor and the Navy Base)

311- 50 square miles (Half of Whidbey Island, all of Camano Island)

451 – 100 square miles (most of Whidbey Island)

5More than 100 square miles (all of Whidbey Island and more)

3.MAGNITUDE

Analysis Definitions:

PROPERTY:Private residences and commercial property of all types.

INFRASTRUCTURE: Public buildings and facilities, public and private

utilities and services.

1Slight property or infrastructure damage, no injuries.

2Moderate property damage, one or more buildings damaged, and minor

injuries,

3Heavy property damage, several buildings heavily damaged. Infrastructure damaged, some services temporarily disrupted for up to 48 hours in a limited area. Numerous injuries, possible casualties.

4Extensive property damage, buildings destroyed. Some services temporarily disrupted for periods over 72 hours in a much wider area. Many injuries, over 10 casualties. (A Nisqually-like quake centered in Island County.)

5Major destruction of property and infrastructure over a wide area. Services disrupted and not expected to return, many injuries, more than 10 casualties (A Katrina-like disaster).

4.CALCULATING IMPACT AND PRIORITY

HAZARD INDEX SCORE = (FREQUENCY + AREA IMPACTED) x MAGNITUDE

WORKSHEET #1: HAZARD RISK ANALYSIS AND ASSESSMENT

Hazard

/

Frequency

/

Area Impacted

/

Magnitude

/

Hazard Index Score

Avalanche

Drought
Earthquake
Flood
Landslide
Severe Storms
Tsunami
Volcano
Interface Fire

Later as a group, we will add personal experience to the hazard index score to further refine the importance or priority of each hazard as it may impact Island County.

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Hazard AnalysisAugust 2006